The major hypothesis of this proposal is that ventricular restraint therapy reduces transmural pressure, end-diastolic volume, and myocardial oxygen consumption to promote reverse remodeling in a dilated failing heart. Prior animal and initial clinical studies demonstrate the promise and feasibility of ventricular restraint therapy, however many questions remain. Our lab has developed a novel ventricular restraint device capable of quantitative ventricular restraint through the use of an epicardial balloon. Our first specific aim is to measure transmural pressure and left ventricular volume throughout the cardiac cycle, derive the pressure-volume relationship and calculate the pressure-volume area using quantitative ventricular restraint in a normal ovine heart. This aim will demonstrate the effect of ventricular restraint on ventricular mechanics and energetics in a normal heart. We will also examine the acute effect of ventricular restraint on myocardial perfusion. Our second aim is to perform these same measurements in an ovine post-infarcted model of dilated cardiomyopathy. We will perform serial measurements over a 3-month longitudinal study to evaluate end-diastolic volume, ventricle contractility, myocardial perfusion, and evidence of reverse remodeling in ventricular restraint versus control animals. Successful completion of these aims will, lead to a better understanding of the effect of ventricular restraint on ventricular physiology.